Unstructured databases are becoming a popular alternative to conventional relational databases due to the relaxed format for data storage and the wider range of data structures that may be stored. In contrast to conventional relational databases, where strong typing imposes data constraints to adhere to a predetermined row and column format, unstructured databases impose no such restrictions.
Unstructured databases have no formal field or record structure, and may be more accurately characterized as a collection of facts. Unlike their structured counterparts, such as a SQL (Structured Query Language) database, which denotes data in fixed length fields enumerated in records in a tabular form, an unstructured database labels fields for storing values in a document. A set of documents defines a collection, in which the documents in a collection may share some, none, or all of a particular field. The document-based arrangement of unstructured databases stores the documents in a sequential order, typically in a sequence of readable characters with delimiters to denote fields (i.e. Unicode, ASCII, or similar). Each document stores a set of fields of the document together. Accordingly, reading a common field from a range of documents typically involves parsing each of the documents and retrieving the desired field. In a large collection having many documents, the volume of parsed documents can be substantial.